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Lecture 5, Sept 24.docx

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Psychology 2135A/B
Marcie Penner- Wilger

Lecture 5. Sept 24 The brain challenge -cognitive science has often ignored the question how is thinking performed in the brain? Why? -functionalism and multiple realizability (multiple instantiation) -hardware (brain, computer) less important than the software -we didn’t really know enough about how the brain works -new methods for brain research increasing knowledge (PET, MRI, fMRI) Ways to carve up the brain -location -structure -function Talairach coordinates -describe location -independent of individual differences (eg. 3, 27, -5-this would be a certain location in the brain) X, Y, Z (X is positive so its in the right side of the brain, Y is also positive so it is in the front, Z is negative so it is in the bottom) -X goes from left to right (0 is in the middle moving to the right is positive larger values, left is negative larger values -Y is front to back (move towards the front of the brain its larger positive values, moving towards the back of the brain it is larger negative values) -Z top to bottom(top is positive larger values, bottom is negative larger values) *Need to be able to identify where coordinates would be in the brain The cortex -frontal lobe -temporal lobe -occipital lobe -parietal lobe (carved up in terms of structure) *need to know these structures and the structure of a neuron (don’t need to know what they do) –in the windows of the mind and brain reading Brodmann areas -region of cortex -based on cytoarchitecture (based on structure but more precise than just frontal occipital etc.) -#1-52 in each hemisphere -very specific coordinates -carved up in terms of structure (different way to carve up the brain) Methods of brain study -dissection -lesions -electrical recording (EEG) and stimulation -brain scans (PET, MRI, fMRI) Brian Imaging: Anatomy EEG -electroencephalograph -recording of electrical signals from the brain from electrodes hooked up to the scalp -observe spilt second changes of a small brain region (not invasive) -can’t show structure/anatomy -can’t tell what specific regions of the brain do CAT -computerized axial tomography aka CT scan -combines many 2D x-rays to create cross sections of 3D images -advantage: can detect brain damage and local changes in cerebral blood flow during a task -disadvantage: radiation, blurry picture so not fine grained PET -positron emission tomography -injection of radioactive glucose -PET scans absorption of radioactivity from outside the scalp -active brain cells consume more glucose so they are more active which the doctors can see (different colours)-shows which areas are active -advantages: allows researchers to observe deep brain structures (unlike EEG), identifies regions which increased activity disadvantages: injection of radioactive material, not fine grained enough MRI -magnetic resonance imaging -inserted into large magnet -generates signals from hydrogen nuclei -detects physical structures -advantage: more fine grained than CAT, no radiation -disadvantage: doesn’t show function fMRI -functional magnetic resonance imaging -detects changes in blood flow during task -advantage: identify brain regions with increased activity (shows function) -disadvantage: poorer temporal resolution than EEG (gives reading over a longer period of time rather than by the second) -this is the methodology of choice -first participants get and MRI to get the structure then do the fMRI to get the function as well MRI vs. fMRI -MRI studies brain anatomy only get one picture high resolution -fMRI studies brain function measures Blood Oxygenation Level Dependent (BOLD) signal indirect measure of neural activity low resolution must take many images about every 2 seconds for 5 minutes neural activity increases --- > blood oxygen increases ---- > fMRI signal increases Correlation vs. Causation -increased activation in a brain area during a specific task does not mean that the area is necessary to perform the task -just the activity in the brain area is correlated with the task TMS -transcranial magnetic stimulation -stimulate different parts of the cortex (turns off and on parts of the brain) -changes brain activity in area -advantage: evidence of regions used in performing task (rather than correlates) -disadvantage: potential side effects? -temporary brain damage (if they turn on a part of your brain and it is supposed to work during an activity and it doesn’t then they consider
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